Depending on how much of a tinker-er DM you are (and whether you have
DDI) ...
One solution would be to work out what the "Hybrid"* versions of the Vestige Warlock and Shaman would be. And if your player likes it, let him play that.
Good Luck,
Graethynne
*
WotC put out the Hybrid rules as a playtest in
DDI last month. Basically, hybrid characters are a pretty even blend of the two constituent classes with some of the features of each and the ability to gain more. If you'd like to know more "read the book" (or in this case check out
DDI).